The present invention is directed to the field of power driven wheelchairs, in general, and more particularly to an integral joystick display therefor and a method of operating the same.
Power driven wheelchairs which may be of the type manufactured by Invacare Corporation of Elyria, Ohio, for example, generally include right and left side drive wheels driven by a motor controller via respectively corresponding right and left side drive motors, all of which being disposed on the wheelchair. An exemplary illustration of such a motor drive arrangement is shown in the schematic of FIG. 1. Referring to FIG. 1, a motor drive controller 10 which may be an Invacare MK IV™ controller, for example, controls drive motors 12 and 14 which are mechanically linked respectively to the right side and left side drive wheels of the wheelchair. The controller 10 includes a microcontroller 15 which may be programmed with a plurality of drive programs, each suited for a particular operating environment of the wheelchair.
A user interface 16 Which may include a joystick 18 and selection switches (not shown) operable by a user is also disposed on the Wheelchair in a convenient location to the user. The user interface 16 is generally interfaced to the microcontroller 15 over a two wire serial coupling 20 to permit the user to select a drive program appropriate for operating the wheelchair in its environment and to adjust the direction and speed of the wheelchair within the selected drive program. In the present example, a main program of the microcontroller 15 which may contain the plurality of drive programs is stored in a non-volatile memory 19, like a read only memory (ROM), for example, -which may be integrated into the microcontroller 15 or may be a separate component thereof.
The motor controller 10 is generally powered by a battery source 22, which may be 24 volts, for example, also disposed on the wheelchair. The drive motors 12 and 14 may be of the permanent magnet type and may be either a gearless, brushless AC motor or a brush type DC motor. The microcontroller 15 is interfaced and responsive to the user interface 16 to control drive signals 24 and 26 to motors 12 and 14, respectively, via a power switching arrangement configured in accordance with the motor type being driven. The power switching arrangement may be powered by the 24V battery 22. Thus, as the user adjusts the speed and direction of the wheelchair via the joystick of interface 16, appropriate drive signals 24 and 26 are controlled by motor controller 10 via microcontroller 15 to drive the motors 12 and 14 accordingly.
Motor controller 10 generally controls motor speed to the user setting utilizing a closed loop controller programmed in the microcontroller 15. Actual speed of each motor 12 and 14 may be derived from signals 28 and 30 respectively sensed therefrom. For example, for AC motors, a Hall Effect sensor may be disposed at the motor for sensing and generating a signal representative of angular position. The signals 28 and 30 are coupled to the microcontroller 15 which may be programmed to derive motor speed from a change in angular position for use as the actual speed feedback signal for the closed loop speed control of the motor. For DC motors, the voltage Va across the armature and armature current Ia may be sensed from each motor 12 and 14 and provided to the microcontroller 15 via lines 28 and 30, respectively. Microcontroller 15 may under programmed control derive the actual speed of each motor 12 and 14 from the respective voltage Va and current Ia measurements thereof for use as the speed feedback signal for the respective closed loop speed control of each motor 12 and 14.
In addition, interaction with the motor controller 10 is performed through a remote programmer 34 which may be electrically coupled to a port of the microcontroller 15 via signal lines 36, for example. Each remote programmer 34 may include a screen 38 for displaying interactive text and graphics and a plurality of pushbuttons 40 for communicating with the microcontroller 15 which is programmed to interact with the programmer 34. A dealer is generally provided with one or more remote programmers for rendering the wheelchair unique to the user's safe operating capabilities.
Present joystick interface units 16, like the joystick unit interfaced to Invacre's MK IV controller, for example, do not have an interactive display, but rather are only capable of displaying an indication of battery discharge which may be a line bar representative of the charge remaining on the battery 22, for example. It is desirable from both a user and dealer standpoint to have a display which may selectively display screen images of current operational parameters of the wheelchair. Display of such operational parameters of the wheelchair will enhance the ability to know when to replace and service certain components of the wheelchair.
The present invention provides such a display integral to a joystick unit which is already interfaceable to and operable with the microcontroller 15 for hands-on control to render a more convenient and less costly add-on display.